image scaling problems: due to PNG format - Page 2

fbrzvnrnd · 03-03-2017, 11:44 PM

Quote:

Originally Posted by JSWolf

That's why you use % as needed. the problem is that ADE does not do media queries. Also, if you are selling the ePub, you'll have no idea the hardware people are using. Can be a smartphone, tablet, Reader, computer all with different resolution screens. So no, you cannot scale for any specific screen.

If I remember right ADE supports media queries in EPUB3. I got some problems with iBooks desktop.

stumped · 03-04-2017, 01:03 AM

i did observe that the book in question rendered better in ADEafter running it through a calibre epub to epub conversion ( which added a css class for img with some 100% settings )
could the ADE support for media queries in epub 3 be a version thing. i.e. you need version x,x or later ?
can I have safely multiple version of ADE installed in order to test that

GrannyGrump · 03-05-2017, 11:44 PM

I am curious to know about the image sizes you are working with here.
What is the resolution//pixel width and height of the largest image? What is the file size in kb?

Are these color/photorealistic images? Line drawings? Black and white?

There are some things that can be done to optimize the image size/file size, but different types of image have different requirements.

16-million color (24bpp) PNG gives very good results for almost any image, but the file size can be really huge.

Line art can be saved as 8bit 256-color/greyscale png for much smaller files, they don't need 16-million color. (You can even use "palleted" image, reducing the number of colors to as low as 32, and then save as a 256-color png -- fewer colors will mean a smaller image. Don't go as low as 16-colors though --- some older Sony readers, and perhaps others, cannot render 16-colors correctly and display an awful mess. Also avoid the "Web-safe" pallet, it gives truly ugly results.

256-color Png cannot render photos and gradients well, you will see "banding" or what is sometimes called the "posterized" effect. Those kind of images can be saved as jpeg, with the least compression you can afford to keep the compression artifacts to a minimum, and still get a smaller file size. Compressed jpeg almost always gives a smaller file-size than png, but also a lower quality.

If you down-size image resolution, you might check out a very simple little utility called Color Quantizer -- it offers a range of different algorithms for resizing, and with experimentation you can get really nice-looking results. (You DO NOT want to use "Pixel Resizing" --- it gives the worst results in the world.)
http://x128.ho.ua/color-quantizer.html ---- site is in Russian, thank heaven for Google Translate!, but the application GUI is in English.

stumped · 03-06-2017, 01:24 AM

Quote:

Originally Posted by GrannyGrump

I am curious to know about the image sizes you are working with here.
What is the resolution//pixel width and height of the largest image? What is the file size in kb?

as already posted see #1 #2, each image is about 6Mb, with about 50 in the book, 24 or 32 bit colour according to sigil image properties, dimensions previously posted, see earlier posts. i have not checked eery image, but I think they areaa ll of similar size & dimensions. they are illustrations, not photos, i.e. created individually by graphic artist

this is a commercial book, not my creation, so I cannot upload extracts

fbrzvnrnd · 03-06-2017, 02:22 AM

Quote:

Originally Posted by stumped

as already posted see #1 #2, each image is about 6Mb, with about 50 in the book, 24 or 32 bit colour according to sigil image properties, dimensions previously posted, see earlier posts. i have not checked eery image, but I think they areaa ll of similar size & dimensions. they are illustrations, not photos, i.e. created individually by graphic artist

this is a commercial book, not my creation, so I cannot upload extracts

6 MB. Have you tried the loading speed with normal e-readers? It seems to me really big files.

Fabrizio

stumped · 03-06-2017, 02:30 AM

This thread was purely for intellectual curiosity, as to lack of image scaling in ADE. I am not really curious about device loading speeds. On my high spec pc and tablet it is fine. As previously stater there is anyway one image per chapter only, so a device that lods single chapters should cope.
It is a loan book, i will be returning and deleting it very soon.

GrannyGrump · 03-06-2017, 02:54 AM

if these illustrations consist of areas of "flat" colors, they can probably be reduced to 8-bit 256-color quite nicely. If gradients, probably not. Or, if absolutely accurate colors are *critical*, you might not want to disturb them. (although colors displayed electronically are seldom going to be very accurate, it is the nature of the beast for different rendering engines to show different results)

You might experiment with converting to jpeg, with a considerable saving in file-size. I did a batch recently. For example --- a smallish illustration --- png 765x1200 px at 1.5 MB--- converted to jpeg with 15% compression (or as some graphics editors dub it, "85% Quality"), resulting in a 280 KB file. It looks pretty darn good, too! (this was an image extracted from a scan of a 1906 vintage book, so it was far from perfect to begin with). I also saved the same image as PNG reduced to 8-bit 256 color, resulting in a 470 KB file --- larger than the jpeg, but still very much smaller than the 24-bit.

But png does give a much cleaner image than jpeg, and doesn't spit stray pixels into adjoining colors. So you juggle your priorities --- file-size vs. quality.

I don't know if the attachments will give a clear view, but it seems to me that under normal conditions, the quality for both is acceptable. Compare to the "Original" (had to crop to meet upload limit), see what you think.

stumped · 03-06-2017, 03:06 AM

Quote:

Originally Posted by fbrzvnrnd

6 MB. Have you tried the loading speed with normal e-readers? It seems to me really big files.

Fabrizio

I dont own a normal e reader, if by that you mean epub e ink. I am not interested in improving the book as i will not be keeping it. I just wanted to understand why it did not display well in ade or in moon reader.

fbrzvnrnd · 03-06-2017, 05:30 AM

Ok, sorry, I thought you wanted to build a new ebook starting from the old one. If this is a commercial EPUB, I think it is a bad-project.

03-05-2017, 11:44 PM	#18
GrannyGrump Obsessively Dedicated... Posts: 3,221 Karma: 35037583 Join Date: May 2011 Location: PA {back in the usa!} Device: Sony PRS-T2, ADE on PC	I am curious to know about the image sizes you are working with here. What is the resolution//pixel width and height of the largest image? What is the file size in kb? Are these color/photorealistic images? Line drawings? Black and white? There are some things that can be done to optimize the image size/file size, but different types of image have different requirements. 16-million color (24bpp) PNG gives very good results for almost any image, but the file size can be really huge. Line art can be saved as 8bit 256-color/greyscale png for much smaller files, they don't need 16-million color. (You can even use "palleted" image, reducing the number of colors to as low as 32, and then save as a 256-color png -- fewer colors will mean a smaller image. Don't go as low as 16-colors though --- some older Sony readers, and perhaps others, cannot render 16-colors correctly and display an awful mess. Also avoid the "Web-safe" pallet, it gives truly ugly results. 256-color Png cannot render photos and gradients well, you will see "banding" or what is sometimes called the "posterized" effect. Those kind of images can be saved as jpeg, with the least compression you can afford to keep the compression artifacts to a minimum, and still get a smaller file size. Compressed jpeg almost always gives a smaller file-size than png, but also a lower quality. If you down-size image resolution, you might check out a very simple little utility called Color Quantizer -- it offers a range of different algorithms for resizing, and with experimentation you can get really nice-looking results. (You DO NOT want to use "Pixel Resizing" --- it gives the worst results in the world.) http://x128.ho.ua/color-quantizer.html ---- site is in Russian, thank heaven for Google Translate!, but the application GUI is in English. Last edited by GrannyGrump; 03-05-2017 at 11:54 PM.

03-06-2017, 02:54 AM	#22
GrannyGrump Obsessively Dedicated... Posts: 3,221 Karma: 35037583 Join Date: May 2011 Location: PA {back in the usa!} Device: Sony PRS-T2, ADE on PC	if these illustrations consist of areas of "flat" colors, they can probably be reduced to 8-bit 256-color quite nicely. If gradients, probably not. Or, if absolutely accurate colors are critical, you might not want to disturb them. (although colors displayed electronically are seldom going to be very accurate, it is the nature of the beast for different rendering engines to show different results) You might experiment with converting to jpeg, with a considerable saving in file-size. I did a batch recently. For example --- a smallish illustration --- png 765x1200 px at 1.5 MB--- converted to jpeg with 15% compression (or as some graphics editors dub it, "85% Quality"), resulting in a 280 KB file. It looks pretty darn good, too! (this was an image extracted from a scan of a 1906 vintage book, so it was far from perfect to begin with). I also saved the same image as PNG reduced to 8-bit 256 color, resulting in a 470 KB file --- larger than the jpeg, but still very much smaller than the 24-bit. But png does give a much cleaner image than jpeg, and doesn't spit stray pixels into adjoining colors. So you juggle your priorities --- file-size vs. quality. I don't know if the attachments will give a clear view, but it seems to me that under normal conditions, the quality for both is acceptable. Compare to the "Original" (had to crop to meet upload limit), see what you think. Attached Thumbnails Last edited by GrannyGrump; 03-06-2017 at 10:07 PM.

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03-04-2017, 01:03 AM	#17
stumped Wizard Posts: 3,305 Karma: 10259306 Join Date: May 2016 Device: kobo forma, Kobo Libra, Huawei media Tab, fire HD10, PW3 HDX8.9,	i did observe that the book in question rendered better in ADEafter running it through a calibre epub to epub conversion ( which added a css class for img with some 100% settings ) could the ADE support for media queries in epub 3 be a version thing. i.e. you need version x,x or later ? can I have safely multiple version of ADE installed in order to test that

03-06-2017, 02:30 AM	#21
stumped Wizard Posts: 3,305 Karma: 10259306 Join Date: May 2016 Device: kobo forma, Kobo Libra, Huawei media Tab, fire HD10, PW3 HDX8.9,	This thread was purely for intellectual curiosity, as to lack of image scaling in ADE. I am not really curious about device loading speeds. On my high spec pc and tablet it is fine. As previously stater there is anyway one image per chapter only, so a device that lods single chapters should cope. It is a loan book, i will be returning and deleting it very soon.

03-06-2017, 05:30 AM	#24
fbrzvnrnd Fanatic Posts: 559 Karma: 400004 Join Date: Feb 2009 Device: ONYX M96	Ok, sorry, I thought you wanted to build a new ebook starting from the old one. If this is a commercial EPUB, I think it is a bad-project.